Voice packet communications system with communications quality evaluation function

ABSTRACT

A voice packet communications system which objectively evaluates the voice quality in real time. Voice packets received from a network are input into an adjustment circuit. The adjustment circuit evens out the periods of the voice packets, detects the drop-out of voice packets, and inserts substitute packets in the voice packet sequence. Furthermore, the adjustment circuit outputs the number of voice packets that have dropped out, the number of substitute packets that have been inserted, and the number of voice packets that have accumulated inside the circuit, as quality information in each monitoring period. A decoding circuit converts the voice packets adjusted by the adjustment circuit into voice information. A judgement circuit calculates an index that indicates the communications quality of the voice packets from the quality information using a specified calculation formula.

This application is a continuation of U.S. patent application Ser. No.11/39,884, filed Jan. 24, 2005, which is a divisional of U.S.application Ser. No. 09/989,402 filed Nov. 21, 2001 now U.S. Pat. No.6,885,659 the subject matter of which application is incorporated hereinby reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a technique for evaluating thecommunications quality of voice packets. For example, the presentinvention can be applied to internet telephony or the like.

2. Description of Related Art

Techniques for voice communications utilizing networks such as theinternet or the like are known. In voice communications of this type,voice information is compressed and encoded; this information is furtherformed into packets, and is transmitted via a network.

In the case of such voice communications via a network, the voicequality deteriorates as a result of packet dropout (i.e., packet loss),delay in transmission, fluctuation in transmission delay (i.e., jitter)and the like. The frequency of occurrence of packet dropout and themagnitude of the fluctuation in transmission delay vary at all timesaccording to the network traffic. Accordingly, the voice quality variesaccording to such variations in frequency and magnitude.

In the case of multi-media communications that handle voice, images andthe like, lossly compression is commonly used as the compression method.For example, a high compression rate of several tens of times to severalhundred times can be obtained by lossly compression. In the case oflossless compression, on the other hand, a compression rate of severalof times can be obtained. However, in the case of data compressed usinglossly compression, there is a high probability that some of theinformation will drop out when the data become to be extracted.Accordingly, a technique for the objective evaluation of the effects ofsuch dropout on communications quality is needed.

Currently, however, no technique exists for the objective measurement ofvoice quality in real time.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a voice packetcommunications system which allows the objective measurement of voicequality in real time.

The voice packet communications system of the first invention comprisesan adjustment circuit which evens out the periods of voice packetsreceived from a network, detects the dropout of voice packets, insertssubstitute packets into the voice packet sequence, and outputs qualityinformation that contains information concerning dropout of the voicepackets and information concerning insertion of the substitute packets;a decoding circuit which converts voice packets adjusted by theadjustment circuit into voice information; and a judgement circuit whichjudges the communications quality of voice packets using qualityinformation.

The first invention makes it possible to measure voice qualityobjectively in real time by judging the communications quality of thevoice packets using quality information.

The voice packet communications system of the second invention comprisesan adjustment circuit which evens out the periods of voice packetsreceived from a network, and inserts substitute packets into the voicepacket sequence; a decoding circuit which converts voice packetsadjusted by the adjustment circuit into voice information; and ajudgement circuit which judges the communications quality of voicepackets by comparing voice information with reference voice informationreceived from the network in accordance with a quality assurance typeprotocol.

The second invention makes it possible to judge the communicationsquality of voice packets objectively in real time by comparing voiceinformation with reference voice information received from the networkin accordance with the quality assurance type protocol.

The voice packet communications system of the third invention comprisesan adjustment circuit which evens out the periods of voice packetsreceived from a network, detects the dropout of voice packets, insertssubstitute packets into the voice packet sequence, and outputs qualityinformation that contains information concerning dropout of the voicepackets and information concerning insertion of the substitute packets;a decoding circuit which converts voice packets adjusted by theadjustment circuit into voice information; and a judgement circuit whichjudges the communications quality of voice packets by comparingreference voice information that has been modified according to thequality information with unmodified reference voice information.

The third invention makes it possible to judge the communicationsquality of voice packets objectively in real time by comparing referencevoice information that has been modified according to qualityinformation with unmodified reference voice information.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the present invention will be describedwith reference to the following appended figures.

FIGS. 1 and 2 are block diagrams which illustrate the construction ofessential parts of a voice packet communications system constituting afirst embodiment of the present invention;

FIG. 3 is a schematic diagram which is used to illustrate the operationof the voice packet communications system of the first embodiment;

FIG. 4 is a block diagram which illustrates the construction ofessential parts of a voice packet communications system constituting asecond embodiment of the present invention;

FIGS. 5, 6 and 7 are block diagrams which illustrate the construction ofessential parts of a voice packet communications system constituting athird embodiment of the present invention;

FIG. 8 is a schematic diagram which is used to illustrate the operationof the voice packet communications system of the third embodiment;

FIG. 9 is a block diagram which illustrates the construction ofessential parts of a voice packet communications system constituting afourth embodiment of the present invention;

FIGS. 10 and 11 are block diagrams which illustrate the construction ofessential parts of a voice packet communications system constituting afifth embodiment of the present invention;

FIGS. 12, 13 and 14 are schematic diagrams which are used to illustratethe operation of the voice packet communications system of the fifthembodiment;

FIG. 15 is a block diagram which illustrates the construction ofessential parts of a voice packet communications system constituting asixth embodiment of the present invention;

FIG. 16 is a block diagram which illustrates the construction ofessential parts of a voice packet communications system constituting aseventh embodiment of the present invention; and

FIG. 17 is a block diagram which illustrates the construction ofessential parts of a voice packet communications system constituting aneighth embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention are now explained with reference tothe drawings. The size, shape and positional relationship of therespective structural components in the drawings are merely shownschematically such that the present invention may be comprehended, andthe numerical conditions described below are only exemplificationsthereof.

First Embodiment

FIG. 1 is a block diagram which illustrates the construction ofessential parts of the voice packet communications device 100 of thepresent embodiment in schematic form.

The voice packet communications device is constructed according to theVoIP (voice over internet protocol). This communications device 100 isused to perform voice communications in both directions via theinternet. Accordingly, the voice packet communications device comprisesa packet transmitting device and a packet receiving device. Thecommunications device 100 performs packet communications with othercommunications devices via an IP communications network 110 such as theinternet or the like. For example, the communications device 100 isrealized by means of a personal computer.

In the present embodiment, monitoring of the communications quality isperformed only by the packet receiving device, and is not performed bythe packet transmitting device. Accordingly, the construction of thepacket transmitting device is not limited in the present embodiment.Ordinarily, in cases where bi-directional communications are performedvia the internet, the route used in communications in one direction andthe route used in communications in the other direction are the same. Asa result, in these routes, the router used to transmit voice packets isalso the same. Accordingly, it would appear that the results ofcommunications quality evaluation would also be the same in most cases.The reason for this is that a deterioration in communications quality isthought to be caused mainly by the processing capacity of the router. Incases where the processing capacity of the router is low, packet dropoutand delay tend to occur.

As is shown in FIG. 1, the communications device 100 comprises a voicepacket adjustment circuit 101, a voice decoding circuit 102, and acommunications quality judgement circuit 103.

The voice packet adjustment circuit receives voice packets PI from thenetwork 110, and outputs these voice packets to the voice decodingcircuit 102 at specified time intervals. In a communications networksuch as the internet or the like, the reception interval of the packetsis not guaranteed. Accordingly, the communications device 100 receivesvoice packets PI at irregular intervals. Consequently, in order torealize high-quality voice communications, the voice packet adjustmentcircuit 101 converts the voice packets PI received at irregularintervals into a voice packet sequence with a uniform time spacing. Inthe following description, this time spacing will be referred to as thedecoding period T. Specifically, voice packets PO are output from thevoice packet adjustment circuit 101 at every decoding period T. Inaddition, at every monitoring period TE, the voice packet adjustmentcircuit 101 outputs the number D of dropped-out voice packets PI, thenumber I of inserted substitute voice packets, and the number B ofinternally accumulated voice packets PI. The drop-out number D, theinsertion number I and the cumulative number B will be described indetail later.

The voice decoding circuit 102 receives voice packets PO from the voicepacket adjustment circuit 101. Voice information is stored in acompressed and encoded state in each voice packet PO. The voice decodingcircuit 102 extracts and decodes the voice information of the voicepackets PO. As a result, voice information S is produced. The quality ofthe voice information S is improved by fixing the reception period ofthe voice packets PO. For example, the voice decoding circuit operatesaccording to a standard such as G.729 or G.723.1 of ITU-T (InternationalTelecommunications Union-Telecommunications Service Sector) Standards.In the case of G.729, the decoding period T is 0.01 seconds; in the caseof G.723.1, the decoding period T is 0.03 seconds.

The communications quality judgement circuit 103 inputs the drop-outnumber D, the insertion number I and the cumulative number B from thevoice packet adjustment circuit 101 in each monitoring period TE. Inaddition, the judgement circuit 103 calculates a communications qualityindex E using the input information D, I and B for each monitoringperiod TE. The details of the method used to calculate thecommunications quality index E will be described later.

Finally, the voice information is converted into voice by the voicedecoding circuit 102. Accordingly, even if a portion of the voice datadrops out when the voice information is extracted and decoded, there isno problem as long as this drop-out only occurs to an extent that cannotbe detected by the human auditory sense. Accordingly, in ordinary voicecommunications, more importance is attached to increasing thecompression rate than to suppressing data loss. The efficiency of datacommunications is substantially increased as the size of the voice datais reduced; accordingly, deterioration in communications quality causedby voice delay is suppressed. Consequently, in most cases, losslycompression is used as the compression system. In cases where thedrop-out and delay of voice data are extremely prevalent, i.e., in caseswhere these phenomena occur to an extent that can be distinguished by ahuman being, the communications quality deteriorates. The communicationsdevice 100 of the present embodiment can calculate a numerical value,i.e., the communications quality index E, for the objective evaluationof this communications quality. Using this communications quality indexE, the voice quality can be distinguished objectively and in real time.

FIG. 2 is a block diagram which illustrates an example of the internalconstruction of the voice packet adjustment circuit 101 in schematicterms.

As is shown in FIG. 2, the voice packet adjustment circuit 101 comprisesa drop-out detector 201, a packet writer 202, an FIFO (first-infirst-out) memory 203, a packet reader 204, a read-out processor 205, areception state detector 206, a subtractor 207, a period generator 208and a substitute data generator 209.

The drop-out detector 201 receives voice packets PI from the network110. Then, this detector 201 detects whether or not there is anydrop-out in the voice packets PI thus received. Serial numbers, timestamps or the like contained in the voice packets PI are used for thisdetection. These serial numbers or time stamps are stored in the voicepackets PI by the packet transmitting device. For example, in a casewhere a voice packet P1 in which the number 1 is stored, a voice packetP2 in which the number 2 is stored, and a voice packet P3 in which thenumber 3 is stored, are received in this order, and a voice packet P5 inwhich the number 5 is stored is subsequently received, it is judged thata voice packet in which the number 4 is stored has dropped out in thenetwork 110. The result of the detection of this drop-out is output as adetection signal E1. Specifically, each time that such a drop-out isdetected, the drop-out detector 201 outputs a detection signal E1 to thereception state detector 206.

The packet writer 202 successively receives voice packets PI from thedrop-out detector 201. The packet writer 202 writes these voice packetsinto the FIFO memory 203. Each time that the packet writer 202 performswriting into the FIFO memory 203, a write signal E2 is output to thesubtractor 207.

The FIFO memory 203 holds voice packets PI according to the order inwhich these voice packets are written into the memory. Specifically, theFIFO memory 203 constructs a voice packet queue. The number of queuesthus constructed is one. The FIFO memory 203 is realized by means of amemory that has a sufficient capacity, e.g., a random access memory.

The packet reader 204 inputs signals to which decoding period T has beenapplied from the period generator 208. Then, the packet reader 204 readsout one voice packet from the FIFO memory 203 for each decoding periodT. The voice packets thus read out are output to the read-out processor205. Furthermore, the packet reader 204 outputs a read-out signal E3 tothe subtractor 207 each time that the packet reader 204 performsread-out from the FIFO memory 203. In cases where no voice packets arestored in the FIFO memory 203, the packet reader 204 outputs invaliddata constructed from a specified bit pattern to the read-out processor205 for each decoding period T.

The read-out processor 205 successively receives voice packets orinvalid data from the packet reader 204. Furthermore, when the read-outprocessor 205 receives a voice packet, the read-out processor 205 sendsthis voice packet to the voice decoding circuit 102 “as is”. On theother hand, when the read-out processor 205 receives invalid data, theread-out processor 205 outputs insertion signals E4 and E5, and alsoreceives a substitute voice packet PP. The substitute voice packet PP isa voice packet which stores specified voice data corresponding tomicro-noise or the like. This packed PP is sent to the voice decodingcircuit 102 instead of invalid data. Accordingly, a voice packet PI orsubstitute voice packet PP is output from the read-out processor 205 asa packet PO for each decoding period T. As a result of the insertion ofa substitute voice packet PP, voice information S in which factors thatcause an unpleasant sensation to human beings such as voiceinterruptions or the like are ameliorated, i.e., voice information Swith a high communications quality, can be produced by the voicedecoding circuit 102.

The reception state detector 206 outputs a drop-out number D, insertionnumber I and cumulative number B for each monitoring period TE. Themonitoring period TE is the period with which the communications qualityis monitored. This monitoring period TE is set as an integral multipleof the decoding period T. The drop-out number D is the number ofdropped-out voice packets detected by the drop-out detector 201. Thereception state detector 206 judges the drop-out number D by countingthe number of times that a signal E1 is received from the drop-outdetector 201. The insertion number I is the number of substitute voicepackets PP inserted into the voice packet sequence by the read-outprocessor 205. The reception state detector 206 judges the insertionnumber I by counting the number of times that a signal E4 is receivedfrom the read-out processor 205. The cumulative number B is the numberof voice packets that have stored in the FIFO memory 203, i.e., thequeue length. The reception state detector 206 receives the cumulativenumber B from the subtractor 207. After these values D, I and B havebeen output, the counters that count the values D and I are reset.

The subtractor 207 inputs the signals E2 and E3. Furthermore, thesubtractor 207 calculates the cumulative number B using these signals E2and E3, and outputs this cumulative number B to the reception statedetector 206. The intervals at which the voice packets are received arelong in some cases and short in other cases. For example, if the delayof a certain voice packet is small and the delay of the next voicepacket is large, the reception interval is lengthened. Conversely, ifthe delay of a certain voice packet is large and the delay of the nextvoice packet is small, the reception interval is shortened. In bothcases, the read-out processor 205 attempts to read out the voice packetswith a fixed period T. Accordingly, if a state in which the timeinterval of voice packet reception is small continues, the number ofvoice packets stored in the FIFO memory 203 (i.e., the queue length) isincreased; on the other hand, if a state in which the time interval ofvoice packet reception is large continues, the number of voice packetsstored in the FIFO memory 203 decreases. For example, the calculation ofthe cumulative number B can be accomplished using two counters and onesubtraction device. One of the counters counts the number of signals E2input into the subtractor 207. The other counter counts the number ofsignals E3 input into the subtractor 207. Furthermore, the subtractiondevice subtracts the count value of the second counter from the countvalue of the first counter for each monitoring period TE. The result ofthis subtraction is the cumulative number B.

The period generator 208 generates a signal that determines the decodingperiod T and a signal that determines the monitoring period TE, andoutputs these signals.

The substitute data generator 209 outputs one of the abovementionedsubstitute voice packets PP each time that a signal E5 is input from theread-out processor 205.

Next, the communications quality judgement circuit 103 will be describedin detail.

As was described above, the communications quality judgement circuit 103calculates the communications quality index E for each monitoring periodTE using the drop-out number D, the insertion number I and thecumulative number B input from the voice packet adjustment circuit 101.

The drop-out of voice packets PI naturally causes a deterioration in thequality of the voice information S. Furthermore, although the quality ofthe voice information S is improved by the insertion of substitute voicepackets PP as described above, the communications quality in cases wherepackets PP are inserted is worse than the quality obtained in caseswhere there is no need for such insertion. Furthermore, the cumulativenumber B indicates the degree to which the reproduction of voiceinformation transmitted from the packet transmitting device is delayed.Accordingly, the communications quality becomes poorer as the drop-outnumber D, the insertion number I and the cumulative number B increase.

In the present embodiment, the communications quality index E isobtained by calculation using Equation (1) shown below. However, incases where E<0, E is set equal to zero. In Equation (1), N is the ratioof the monitoring period TE to the decoding period T, i.e., TE/T. As wasdescribed above, the monitoring period TE is set as an integral multipleof the decoding period T. Accordingly, N is a positive integer.Furthermore, the values of α, β and γ can be arbitrarily determined. Forexample, in cases where the effects of drop-out of voice packets andinsertion of substitute voice packets PP on the voice quality is large,and the effect of the queue length on the voice quality is small, α andβ are set at large values, and γ is set at a small value. For instance,these values can be set as α=10, β=10 and γ=2.

[E]=5−I×(α/N)−D×(β/N)−B×T×γ  (1)

In cases where the communications quality is in an ideal state, i.e., incases where D, I and B are zero, the value of the index E is 5. On theother hand, in cases where the communications quality is at the poorestlevel, the value of the index E is zero.

Next, the overall operation of the communications device 100 of thepresent embodiment will be described with reference to FIG. 3.

Below, FIG. 3 (A) shows (in schematic form) a sequence of voice packetsP1 through P10 transmitted by the packet transmitting device within themonitoring period TE. FIG. 3 (B) shows (in schematic form) the sequenceof voice packets received by the packet receiving device within themonitoring period TE. Specifically, in the example shown in (A) and (B)of FIG. 3, the voice packets P4, P5 and P9 have dropped out in thenetwork. Below, the overall operation of the communications device 100will be described using a case in which the voice packets P4, P5 and P9have dropped out, and in which no voice packet delay has been generated,as an example.

The packet transmitting device successively transmits the voice packetsP1 through P10 to the packet receiving device. The voice packets P1through P10 received by the packet receiving device are sent to thedrop-out detector 201 installed in the voice packet adjustment circuit101 inside the communications device 100.

When the drop-out detector 201 receives the voice packet P1, thedrop-out detector 201 reads out the serial number, time stamp or thelike that is stored in this voice packet P1, and stores this serialnumber or time stamp internally. Furthermore, the drop-out detector 201sends the voice packet P1 to the packet writer 202. In this case, thedrop-out detector 201 does not output a signal E1. The packet writer 202writes the voice packet P1 into the FIFO memory 203, and also outputs asignal E2. The subtractor 207 increases the count value of the signalsE2 by “1”. The packet reader 204 reads out the voice packet P1 at atiming given by the signal T. Generally, the speed with which the voicedecoding circuit 102 decodes the voice packets is set so that this speedcoincides with the speed at which the packet transmitting deviceproduces and outputs the voice packets. Accordingly, the period withwhich the packet reader 204 reads out the voice packets is also set sothat this period corresponds to the decoding speed of the voice decodingcircuit 102. Accordingly, the decoding period [T], i.e., the read-outperiod of the packet reader 204, is set so that T=TE/10. The packetreader 204 sends the voice packet P1 that has been read out to theread-out processor 205, and also outputs a signal E3. The subtractor 207increases the count value of the signals E3 by “1”. the read-outprocessor 205 outputs the voice packet P1 to the voice decoding circuit102 as a packet PO without outputting signals E4 or E5.

After time T has elapsed following the reception of the voice packet P1,the drop-out detector 201 receives the voice packet P2. The drop-outdetector 201 reads the serial number or the like that is stored in thisvoice packet P2, and judges whether or not drop-out has occurred. Inthis case, since no drop-out has occurred; a signal E1 is not output.Subsequently, the voice packet P2 is sent to the packet writer 202. Thepacket writer 202 writes this voice packet P2 into the FIFO memory 203,and also outputs a signal E2. The subtractor 207 increases the countvalue of the signals E2 by “1”. The packet reader 204 reads out thevoice packet P2, sends the read-out voice packet P2 to the read-outprocessor 205, and outputs a signal E3. The subtractor 207 increases thecount value of the signals E3 by “1”. The read-out processor 205 thenoutputs the voice packet P2 to the voice decoding circuit 102 as apacket PO without outputting signals E4 or E5.

When the voice packet P3 is received, the drop-out detector 201, packetwriter 202, FIFO memory 203, packet reader 204, read-out processor 205and subtractor 207 perform the same operations as when the voice packetP2 was received.

After time T has elapsed following the reception of the voice packet P3,the drop-out detector 201 does not receive the next voice packet. Thereason for this is that the voice packet P4 has dropped out in thenetwork. Accordingly, the packet writer 202 does not write a voicepacket or output a signal E2. However, as was described above, thepacket reader 204 attempts to read out a voice packet from the FIFOmemory 203 when a signal T is input. In this case, no voice packet isstored in the FIFO memory 203; accordingly, the packet reader 204 sendsinvalid data to the read-out processor 205. The read-out processor 205outputs signals E4 and E5, receives a substitute voice packet PP, andthen outputs this substitute voice packet PP as a voice packet PO. Thereception state detector 206 increases the count value of the signals E4by “1”.

The voice packet P5 has also dropped out in the network. Accordingly,when the next signal T is input, the packet reader 204 attempts to readout a voice packet from the FIFO memory 203. In this case, no voicepacket is stored in the FIFO memory 203; accordingly, the packet reader204 again sends invalid data to the read-out processor 205. The read-outprocessor 205 outputs signals E4 and E5, receives a substitute voicepacket PP, and outputs this substitute voice packet PP as a voice packetPO. The reception state detector 206 increases the count value of thesignals E4 by “1”.

Subsequently, the drop-out detector 201 receives the voice packet P6.The drop-out detector 201 reads out the serial number of the like thatis stored in this voice packet P5. Then, the drop-out detector 201recognizes that the two voice packets P4 and P5 have dropped out, andoutputs two signals E1. The reception state detector 206 increases thedrop-out count value D by “2”. Afterward, the voice packet P6 is sent tothe packet writer 202. The packet writer 202 writes this voice packet P6into the FIFO memory 203, and outputs a signal E2. The subtractor 207increases the count value of the signals E2 by “1”. The packet reader204 reads out the voice packet P6 from the FIFO memory 203, sends theread-out voice packet P6 to the read-out processor 205, and outputs asignal E3. The subtractor 207 increases the count value of the signalsE3 by “1”. The read-out processor 205 then outputs the voice packet P6to the voice decoding circuit 102 as a packet PO without outputtingsignals E4 or E5.

When the voice packets P7 and P8 are received, the drop-out detector201, packet writer 202, FIFO memory 203, packet reader 204, read-outprocessor 205 and subtractor 207 perform the same operations as when thevoice packets P1 through P3 were received.

When then next signal T is input, the packet reader 204 attempts to readout a voice packet from the FIFO memory 203. However, since the voicepacket P9 has dropped out in the network, no voice packet is stored inthe FIFO memory 203. Accordingly, the packet reader 204 sends invaliddata to the read-out processor 205. The read-out processor 205 outputssignals E4 and E5, receives a substitute voice packet PP, and outputsthis substitute voice packet PP as a voice packet PO. The receptionstate detector 206 increases the count value of signals E4 by “1”.

Next, the drop-out detector 201 receives the voice packet P10. Thedrop-out detector 201 reads out the serial number or the like that isstored in this voice packet P10. Then, the drop-out detector 201recognizes that the voice packet P9 has dropped out, and outputs onesignal E1. The reception state detector 206 increases the drop-out countvalue D by “1”. Subsequently, the voice packet P10 is sent to the packetwriter 202. The packet writer 202 writes this voice packet P10 into theFIFO memory 203, and outputs a signal E2. The subtractor 207 increasesthe count value of the signals E2 by “1”. The packet reader 204 readsout the reads out the voice packet P10 from the FIFO memory 203, sendsthe read-out voice packet P10 to the read-out processor 205, and outputsa signal E3. The subtractor 207 increases the count value of the signalsE3 by “1”. The read-out processor 205 outputs the voice packet P10 tothe voice decoding circuit 102 as a packet PO without outputting asignal E4 or E5.

When the monitoring period TE elapses, the subtractor 207 sends thedifference between the count value of the signals E2 and the count valueof the signals E3, i.e., the cumulative number B, to the reception statedetector 206. The reception state detector 206 sends the drop-out numberD, the insertion number I and the cumulative number B to thecommunications quality judgement circuit 103. As will be seen from theabovementioned description, the drop-out number D and insertion number Iare both “3”. Furthermore, since there is no voice packet delay in thisexample of operation, the cumulative number B is “0”.

The communications quality judgement circuit 103 substitutes thesevalues D, I and B into the abovementioned Equation (1), and calculatesthe communications quality index E. Furthermore, in this example ofoperation, N is 10. Accordingly, assuming that α=10, β=10, γ=2 andT=0.01, then the calculation result of Equation (1) is “−1”. As wasdescribed above, in cases where the calculation result is a negativevalue, the communications quality index E is replaced by “0”. As aresult, it is seen that in cases where 30 percent of the voice data islost, the communications quality is in an extremely poor state even ifthere is no delay.

For example, in a case where 10 percent of the voice data is lost andthere is no delay, the communications quality index E is 3.

In this description of the operation, it was assumed that there was nodelay. In cases where there is no delay, a state in which no voicepacket is stored in the FIFO memory 203 when the packet reader 204attempts to read out a voice packet is caused only by the drop-out ofvoice packets. Accordingly, the drop-out number D and the insertionnumber I are the same. On the other hand, in cases where a delay isgenerated in the network, the drop-out number D and insertion number Ino longer coincide. As was described above, a fluctuation in the delay,i.e., jitter, causes a variation in the queue length of the FIFO memory203. In cases where the queue length is zero, a state in which thepacket reader 204 cannot read out a voice packet is generated not onlyby voice packet drop-out, but also by delay. On the other hand, in caseswhere the queue length is “2” or greater, there may be cases in which astate in which the packet reader 204 cannot read out a voice packet isnot generated even if voice packet drop-out should occur.

As was described above, the communications device 100 of the presentembodiment can output, automatically and in real time, a communicationsquality index E that objectively expressed in the communicationsquality. The communications device 100 of the present embodiment isuseful in the development and operation of voice communications systemssuch as internet telephony and the like.

When a voice communications system is to be developed, the developermust repeatedly evaluate the communications quality and modify thesystem. Accordingly, a technique which outputs a communications qualityindex E automatically and in real time greatly reduces the developmenttime and development cost.

In cases where a voice communications system is operated, an improvementin communications quality may be expected as a result of the use of thetechnique of the present invention. Specifically, a constantcommunications quality can be guaranteed by monitoring thecommunications quality in real time, and automatically switching thenetwork path in cases where the communications quality is poor.

Second Embodiment

A second embodiment of the present invention will be described below.

FIG. 4 is a block diagram which illustrates the construction of thecommunications device 400 of the present embodiment in schematic terms.In FIG. 4, symbols that are the same as in FIG. 1 indicate constituentelements that are the same as in FIG. 1.

The communications device 400 of the present embodiment has acommunications quality judgement table 401 instead of a communicationsquality judgement circuit 103 in FIG. 1. For example, the communicationsquality judgement table 401 is realized by means of a non-volatilememory.

A communications quality index E is stored in the communications qualityjudgement table 401 for each combination of the parameters D, I and B.When the drop-out number D, the insertion number I and the cumulativenumber B are input from the voice packet adjustment circuit 101, thecommunications quality judgement table 401 outputs the stored valuecorresponding to the combination of these values D, I and B as acommunications quality index E. The communications quality index E canbe expressed by the following Equation (2):

E=TABLE [I][B][D]  (2)

In the abovementioned first embodiment, the communications quality indexE was determined by calculation using Equation (1). However, in caseswhere it is desired to control the communications quality with a highdegree of precision, it is not easy to obtain the index E bycalculation. The reason for this is that a calculation formula thatshows a high degree of coincidence with the human auditory sense isrequired. Especially in cases where a linear function such as Equation(1) is used, it would appear difficult to achieve a highly precisematching between a quality judgement based on the human auditory senseand the calculated results, i.e., the index E.

In the present embodiment, the communications quality index E isdetermined using the abovementioned communications quality judgementtable 401 instead of a calculation formula. Accordingly, even in caseswhere the index E is a nonlinear function with respect to the parametersD, I and B, an index E that shows a high degree of coincidence with thehuman auditory sense can be produced by means of a device with a simplestructure.

Third Embodiment

Below, a third embodiment of the present invention will be describedwith reference to FIGS. 5 through 8.

FIG. 5 is a block diagram which illustrates the construction of thevoice packet communications system of the present embodiment. As isshown in FIG. 5, this system 500 comprises a packet transmitting device510, a network 520 and a packet receiving device 530.

The packet transmitting device 510 has a voice encoding circuit 511. Thevoice encoding circuit 511 inputs voice information SI from a precedingcircuit, and outputs two types of voice packets PI and PR. Here, thevoice packets PI are the same as the voice packets PI in the first andsecond embodiments. On the other hand, the voice packets PR are voicepackets used for reference. Specifically, the voice packets PR are usedto evaluate the communications quality of the voice packets PI. Thevoice encoding circuit 511 outputs these voice packets PI and PR to thenetwork 520.

The network 520 forms a communications connection between the packettransmitting device 510 and the packet receiving device 530. Here, aprotocol of the type in which quality is not guaranteed is used for thecommunication of the voice packets PI. On the other hand, a protocol ofthe type in which quality is guaranteed, i.e., TCP/IP, is used for thecommunication of the voice packets PR. In other words, the voice packetsPR are transmitted in a communications environment in which there isvery little possibility of the occurrence of delay or jitter.

The packet receiving device 530 receives the voice packets PI and PRfrom the network 520. Furthermore, the packet receiving device 530performs encoding and quality evaluation of the voice packets PI. Thepacket receiving device 530 comprises a voice packet adjustment circuit531, a voice packet accumulating circuit 532, a voice decoding circuit533, a reference voice decoding circuit 534, and a communicationsquality judgement circuit 535.

The voice packet adjustment circuit 531 receives voice packets PI fromthe network 520, and outputs a voice packet PO in each decoding periodT. FIG. 6 shows one example of the internal structure of the voicepacket adjustment circuit 531. In FIG. 6, constituent elements that arelabeled with the same symbols as in FIG. 2 are respectively the same asthe corresponding constituent elements in FIG. 2. The voice packetadjustment circuit 531 does not have any parts that are related to thecommunications quality function. Accordingly, the voice packetadjustment circuit 531 does not have a drop-out detector 201, receptionstate detector 206 or subtractor 207. Consequently, the packet writer202 does not output any signal E2, the packet reader 204 does not outputany signal E3, the read-out processor 205 does not output any signal E4,and the period generator 208 does not output any signal indicating themonitoring period TE.

The voice packet accumulating circuit 532 receives voice packets PR fromthe network 520, and outputs voice packets PT. FIG. 7 shows one exampleof the internal structure of the voice packet accumulating circuit 532.In FIG. 7, constituent elements that are labeled with the same symbolsas in FIG. 6 are respectively the same as the corresponding constituentelements in FIG. 6. The voice packets PT are not used in voice decoding;accordingly, the voice packet accumulating circuit 532 does not have aread-out processor 205 or substitute data generator 209.

The voice decoding circuit 533 receives voice packets PO from the voicepacket adjustment circuit 531, and extracts and decodes the voiceinformation stored in the voice packets PO. As a result, voiceinformation S is produced. A circuit which is the same as the voicedecoding circuit 102 in the first embodiment may be used as the voicedecoding circuit 533.

The reference voice decoding circuit 534 receives voice packets PT fromthe voice packet accumulating circuit 532, and extracts and decodes thevoice information stored in the voice packets PT. As a result, voiceinformation SR is produced. A circuit which is the same as the voicedecoding circuit 533 is used as the decoding circuit 534.

The communications quality judgement circuit 535 evaluates the qualityof the voice information S. The voice information SR is referred to inthis evaluation. The results of this evaluation are output as acommunications quality index E in each standard period TS. For example,the ITU-T Standard P.861 can be used as the evaluation method. By usingthis standard, it is possible to perform a communications qualityevaluation which shows precise agreement with human subjectivity.

Next, the operation of the system 500 of the present embodiment will bedescribed.

FIG. 8 is a schematic diagram which is used to illustrate the procedurethat produces the voice packets PI and PR. As is shown in FIG. 8, thevoice encoding circuit 511 successively produces voice packets PI ineach period T. Furthermore, in each period TS, voice packets PR areproduced by copying a specified number of voice packets PI. In theexample shown in FIG. 8, the period TS is “6×T”, and the specifiednumber is “3”.

As was described above, the voice packets PI are successively sent tothe voice packet adjustment circuit 531 in accordance with a protocol ofthe type in which quality is not guaranteed. Furthermore, the voicepackets PR are sent to the voice packet accumulating circuit 522 inaccordance with a protocol of the type in which quality is guaranteed.In the example shown in FIG. 8, the voice packets PR are transmittedwith the same timing as the corresponding voice packets PI.Specifically, in each period TS, three voice packets PR are successivelytransmitted in the initial time 3×T, and nothing is transmitted in thefollowing time 3×T.

The voice packet adjustment circuit 531 receives the voice packets PI.As was described above, the communications protocol of the voice packetsPI does not guarantee the quality. Accordingly, in most cases, thereception period of the voice packets PI does not agree with thedecoding period T because of delay and jitter generated in the network520. Furthermore, some of the voice packets PI drop out. The voicepacket adjustment circuit 531 adjusts the period of the voice packetsPI, and inserts substitute data if necessary. As a result, voice packetsPO are produced.

The voice packet accumulating circuit 522 receives the voice packets PR.As was described above, the communications protocol of the voice packetsPR guarantees the quality. Accordingly, in most cases, the differencebetween the reception period of the voice packets PR and the decodingperiod T is extremely small, and there is almost no drop-out of voicepackets PR. The voice packet adjustment circuit 532 performs a fineadjustment of the period of the voice packets PR. The finely adjustedvoice packets are output as voice packets PT.

The voice decoding circuit 533 extracts and decodes the voiceinformation of the voice packets PO. As a result, voice information S isproduced. The voice information S is output to the outside of the packetreceiving device 530, and is sent to the communications qualityjudgement circuit 535.

The reference voice decoding circuit 534 extracts and decodes the voiceinformation of the voice packets PT. As a result, voice information SRis produced. The voice information SR is sent to the communicationsquality judgement circuit 535, but is not output to the outside of thepacket receiving device 530.

The communications quality judgement circuit 535 evaluates the qualityof the voice information S using the voice information SR. The resultsof this evaluation are output as a communications quality index E ineach standard period TS.

The communications system 500 of the present embodiment can output,automatically and in real time, a communications quality index E thatobjectively expresses the communications quality. Like thecommunications devices 100 of the first and second embodiments, thecommunications system 500 of the present embodiment is useful in thedevelopment and operation of voice communications systems such asinternet telephony or the like.

In the communications system 500 of the present embodiment, it is alsouseful (for example) to use the voice packets PR only during maintenanceor the like. Ordinarily, communications using a protocol of the type inwhich quality is guaranteed are more expensive than communications usinga protocol of the type in which quality is not guaranteed. In caseswhere the voice packets PR are used only during maintenance, thecommunications cost is reduced.

In the communications system 500 of the present embodiment, there is noneed to add serial numbers of the like to the voice packets PI;furthermore, there is no need to calculate the drop-out number D,insertion number I or cumulative number B. Accordingly, the packettransmitting device 510 and packet receiving device 530 can be made morecompact.

Fourth Embodiment

Below, a fourth embodiment of the present invention will be describedwith reference to FIG. 9.

The present embodiment is an example of a system which has a functionthat evaluates the effect on communications quality of informationdrop-out that occurs when the compressed data become to be extracted.

FIG. 9 is a block diagram which illustrates the construction of thevoice packet communications system 900 of the present embodiment. InFIG. 9, constituent elements that are labeled with the same symbols asin FIG. 5 are respectively the same as the corresponding constituentelements in FIG. 5.

The voice encoding circuit 911 compresses and encodes input voiceinformation SI, and produces voice packets PI using the compressed andencoded voice information. The voice encoding circuit 911 differs fromthe voice encoding circuit 511 in FIG. 5 in that this voice encodingcircuit 911 does not output reference voice packets PR. The voiceencoding circuit 911 transmits one voice packet PI in each decodingperiod T. The voice packets PI are transmitted in accordance with aprotocol of the type in which quality is not guaranteed.

The reference voice transmitting circuit 912 converts input voiceinformation SI into voice packets ST without compressing and encodingthe voice information. Since the voice packets ST are not compressed,these voice packets ST are output at a shorter period than the voicepackets PI. Specifically, in a case where the compression rate of thevoice data stored in the voice packets PI is n, the transmission periodof the voice packets ST is T/n. The voice packets ST are transmitted inaccordance with a protocol of the type in which quality is guaranteed.

The voice packet accumulating circuit 921 receives the voice packets ST.Furthermore, each time that a number of voice packets ST correspondingto the monitoring period TE has accumulated, the voice packetaccumulating circuit 921 outputs the accumulated voice packets ST asvoice information SR1. Next, the overall operation of the system 900 ofthe present embodiment will be described.

As was described above, the voice encoding circuit 911 compresses andencodes the voice information SI, and converts this voice information SIinto voice packets PI. On the other hand, the reference voicetransmitting circuit 912 converts the voice information SI into voicepackets ST without compressing or encoding this information. The packettransmitting device 910 outputs these packets SI and ST to the network520.

The voice packets PI are received by the voice packet adjustment circuit531. The voice packet adjustment circuit 531 adjusts the period of thevoice packets PI, and inserts substitute data if necessary. As a result,voice packets PO are produced. The voice packets PO are input into thevoice decoding circuit 533. The voice decoding circuit 533 extracts anddecodes the voice information of the voice packets PO. As a result,voice information S is produced. The voice information S is output tothe outside of the packet receiving device 530, and is sent to thecommunications quality judgement circuit 535.

The voice packets ST are received by the voice packet accumulatingcircuit 921. As was described above, the voice packet accumulatingcircuit 921 outputs reference voice information SR1 in each monitoringperiod TE. Since the voice packets ST are not compressed and encoded,there is no need for extracting and decoding of these voice packets. Thevoice information SR1 is input “as is” into the communications qualityjudgement circuit 535.

The communications quality judgement circuit 535 evaluates the qualityof the voice information S using the voice information SR1. The resultsof this evaluation are output as a communications quality index E ineach monitoring period TE.

The system 900 of the present embodiment can evaluate the communicationsquality of the voice packets PI using voice information that is notsubjected to compression and extracting. Accordingly, an evaluation ofcommunications quality which takes into account the effect oncommunications quality of the information drop-out that occurs whencompressed data become to be extracted can be performed.

The system 900 of the present embodiment can be utilized in thedevelopment, maintenance and the like of voice communications systems.

Fifth Embodiment

Below, a fifth embodiment of the present invention will be describedwith reference to FIGS. 10 through 14.

The present embodiment is another example of a system which has afunction that evaluates the effect on communications quality ofinformation drop-out that occurs when compressed data become to beextracted.

FIG. 10 is a block diagram which illustrates the construction of thevoice packet communications device 1000 of the present embodiment. InFIG. 10, constituent elements that are labeled with the same symbols asin FIG. 5 respectively indicate constituent elements that are the sameas in FIG. 5. The voice packet communications device 1000 is installedinside a packet receiving device. In the present embodiment, there areno restrictions on the construction of the packet transmitting device.

The voice packet adjustment circuit 1011 adjusts the voice packets PI;i.e., this voice packet adjustment circuit 1011 detects drop-out, makesthe period uniform, and inserts substitute packets, like the voicepacket adjustment circuit 101 of the first embodiment. Furthermore, thevoice packet adjustment circuit 1011 outputs voice packets PO obtainedby these adjustments. In addition, the voice packet adjustment circuit1011 outputs drop-out pattern information IT and substitution patterninformation DT. The details of this drop-out pattern information IT andsubstitution pattern information DT will be described later.

The reference voice generating circuit 1012 produces voice informationSR1. The content of the voice information SR1 is arbitrary. The voiceinformation SR1 is output to the reference voice encoding circuit 1013and communications quality judgement circuit 535.

The reference voice encoding circuit 1013 compresses and encodes thevoice information SR1, and further produces voice packet PB using thiscompressed and encoded voice information.

The network simulating circuit 1014 inputs the voice packets PB, thedrop-out pattern information IT and the substitution pattern informationDT. Furthermore, the network simulating circuit 1014 modifies the voicepackets PB using the information IT and DT. Specifically, the voicepackets PB are modified to voice packets PA that have the same drop-outpattern and same substitution pattern as the voice packets PI.

The reference voice decoding circuit 1015 produces voice information ST1by extracting and decoding the voice packets PA. A circuit with the samestructure as the voice decoding circuit 533 may be used as the referencevoice decoding circuit 1015.

FIG. 11 shows one example of the internal structure of the voice packetadjustment circuit 1011. In FIG. 11, constituent elements labeled withthe same symbols as in FIG. 2 respectively indicate constituent elementsthat are the same as in FIG. 2. As in FIG. 2, the voice packetadjustment circuit 1011 comprises a drop-out detector 201, packet writer202, FIFO memory 203, packet reader 204, read-out processor 205, periodgenerator 208 and substitute data generator 209. However, the packetwriter 202 does not output any signal E2, the packet reader 204 does notoutput any signal E3, and the period generator 208 does not output anysignal indicating the monitoring period TE. The reception state detector1101 inputs a signal E1 from the drop-out detector 201, and inputs asignal E4 from the read-out processor 205, in each decoding period T.Furthermore, the reception state detector 1101 produces and outputsdrop-out pattern information DT and substitute pattern information ITusing these signals E1 and E4.

FIG. 12 is a schematic diagram which shows an example of theconstruction of the drop-out pattern information DT.

FIG. 12 shows an example in which the drop-out pattern information DT isconstructed from 10 bits of data. Below, the period of drop-out patterninformation production, i.e., a period that is 10 times the decodingperiod T, will be referred to as the monitoring period TE. In FIG. 12,“1” indicates that a voice packet has dropped out, and “0” indicatesthat a voice packet has not dropped out. The information DT in FIG. 12indicates that the fourth, fifth and ninth voice packets PI have droppedout.

FIG. 13 is a schematic diagram which shows an example of theconstruction of the substitution pattern information IT. The number ofbits of data in the substitution pattern information IT is the same asthe number of bits of data in the drop-out pattern information DT. InFIG. 13, “0” indicates a received voice packet PI, and “1” indicates asubstitute packet PP. The information IT in FIG. 13 indicates that thesecond, fifth and sixth voice packets are substitute packets PP.

Next, the overall operation of the communications device 1000 of thepresent embodiment will be described with reference to FIG. 14.

The voice packets PI are received by the voice packet adjustment circuit1011. The voice packet adjustment circuit 1011 adjusts the period of thevoice packets PI, and inserts substitute data if necessary. As a result,voice packets PO are produced. The voice packets PO are input into thevoice decoding circuit 533. In addition, the voice packet adjustmentcircuit 1011 produces the drop-out pattern information DT andsubstitution pattern information IT shown in FIGS. 12 and 13, andoutputs this information in each monitoring period TE. The difference inthe detection timing of the drop-out pattern information DT andsubstitution pattern information IT is adjusted by the reception statedetector 1101 inside the voice packet adjustment circuit 1011.

The voice decoding circuit 533 produces voice information S byextracting and decompressing the voice information of the voice packetsPO. This voice information S is output to the outside of the packetreceiving device. In the present embodiment, the voice information S isnot used in the evaluation of the communications quality.

Reference voice information SR1 is output from the reference voicegenerating circuit 1012. This voice SR11 is converted into voice packetsPB by the reference voice encoding circuit 1013.

The network simulating circuit 1014 first inputs 10 voice packets PB ineach monitoring period TE. FIG. 14 (A) shows these 10 voice packets inschematic form. In FIG. 14 (A) the 10 voice packets PB are indicated bythe symbols P1 through P10. These voice packets P1 through P10 arecompared with the drop-out pattern information DT by the networksimulating circuit 1014. FIG. 14 (B) shows one example of the drop-outpattern information DT in schematic form. The network simulating circuit1014 removes voice packets corresponding to the data “1” of theinformation DT from the voice packets PI through P10. In the exampleshown in FIG. 14, the voice packets P4, P5 and P9 are removed. As aresult, a voice packet sequence such as that shown in FIG. 14 (C) isobtained.

Next, the network simulating circuit 1014 compares this voice packetsequence with the substitution pattern information IT. FIG. 14 (D) showsone example of the substitution pattern information IT in schematicform. The network simulating circuit 1014 inserts substitute packets PPinto the voice packet sequence in accordance with the substitutionpattern information IT. In the example shown in FIG. 14 (D), the secondvoice packet is a substitute packet PP. Accordingly, the networksimulating circuit 1014 inserts a substitute packet PP as the secondpacket in the voice packet sequence (see FIG. 14 (C)). As a result, avoice packet sequence such as that shown in FIG. 14 (E) is obtained.Furthermore, in the example shown in FIG. 14 (D) the fifth and sixthvoice packets are substitute packets PP. Accordingly, the networksimulating circuit 1014 inserts substitute packets PP as the fifth andsixth packets in the voice packet sequence. As a result, a voice packetsequence such as that shown in FIG. 14 (F) is obtained.

The voice packets PA thus obtained are converted into voice informationST1 by the reference voice decoding circuit 1015.

The communications quality judgement circuit 535 evaluates the voicequality by comparing the voice information SR1 and ST1. The results ofthis evaluated are output from the communications quality judgementcircuit 535 as an index E which indicates the quality of the voiceinformation S.

As was described above, the device 1000 of the present embodiment makesit possible to evaluate the communications quality while taking intoaccount the effect on communications quality of information drop-outthat occurs when compressed data become to be extracted, without anyneed to transmit uncompressed data via the network 520.

In the device 1000 of the present embodiment, drop-out patterninformation DT and substitution pattern information IT are produced ineach monitoring period TE. However, it would also be possible toconstruct the device 1000 so that data indicating a packet drop-out anddata indicating the insertion of a substitute packet are respectivelysent to the network simulating circuit 1014 from the voice packetadjustment circuit 1011 one bit at a time.

Sixth Embodiment

A sixth embodiment of the present invention will be described withreference to FIG. 15.

FIG. 15 is a block diagram which illustrates the construction of thevoice packet communications device 1500 of the present embodiment. InFIG. 15, constituent elements that are labeled with the same symbols asin FIG. 10 respectively indicate constituent elements that are the sameas in FIG. 10. The voice packet communications device 1500 has a normalvoice decoding circuit 1501. The normal voice decoding circuit 1501produces voice information SL by decoding voice packets PB. This voiceinformation SL is sent to the communications quality judgement circuit535. A circuit which has the same construction as the voice decodingcircuit 533 or 1015 may be used as the normal voice decoding circuit1501.

The overall operation of the communications device 1500 of the presentembodiment will be described below.

As in the fifth embodiment, the voice packet adjustment circuit 1011adjusts the period of the voice packets PI, and inserts substitute dataif necessary. As a result, voice packets PO are produced. In addition,the voice packet adjustment circuit 1011 produces the drop-out patterninformation DT and substitution pattern information IT shown in FIGS. 12and 13, and outputs this information in each monitoring period TE.

The voice decoding circuit 533 produces voice information S byextracting and decoding the voice information of the voice packets PO.This voice information S is output to the outside of the packetreceiving device.

Reference voice information SR1 is output from the reference voicegenerating circuit 1012. This voice ER1 is converted into voice packetsPB by the reference voice encoding circuit 1013. The voice packets PBare sent to the network simulating circuit 1014 and normal voicedecoding circuit 1501.

As in the fifth embodiment, the network simulating circuit 1014 modifiesthe voice packets PB into voice packets PA that have the same drop-outpattern and same substitution pattern as the voice packets PI. The voicepackets PA are converted into voice information ST1 by the referencevoice decoding circuit 1015.

The normal voice decoding circuit 1501 produces voice information SL bydecoding the voice packets PB.

The communications quality judgement circuit 535 evaluates thetelecommunication quality by comparing the voice information SR1 and SL.The results of this evaluation are output from the communicationsquality judgement circuit 535 as an index E which indicates the qualityof the voice information S.

The communications system 1500 of the present embodiment can output,automatically and in real time, a communications quality index E thatobjectively expresses the communications quality. The communicationssystem 1500 of the present embodiment is useful in the development,operation, maintenance and the like of voice communications systems.

The device 1500 of the present embodiment can operate withouttransmitting uncompressed data via the network 520. Accordingly, thecommunications quality index E can be obtained at a low cost.

Seventh Embodiment

A seventh embodiment of the present invention will be described withreference to FIG. 16.

The present embodiment differs from the abovementioned embodiments inthat the packet transmitting device evaluates the communications qualityof the voice packets.

FIG. 16 is a block diagram which illustrates the construction of thevoice packet communications system 1600 of the present embodiment. As isshown in FIG. 16, this system 1600 comprises a packet transmittingdevice 1610, a network 1620 and a packet receiving device 1630.

The packet transmitting device 1610 comprises a voice encoding circuit1611, a network simulating circuit 1612, a local voice decoding circuit1613 and a communications quality judgement circuit 1614.

The voice encoding circuit 1611 compresses and encodes input voiceinformation SI, and produces voice packets PI using this compressed andencoded voice information. The voice encoding circuit 1611 transmits onevoice packet PI in each decoding period T.

The network simulating circuit 1612 inputs the voice packets PI,drop-out pattern information IT (see FIG. 12) and substitution patterninformation DT (see FIG. 13). The drop-out pattern information IT andsubstitution pattern information DT are transmitted to the packettransmitting device 1610 form the packet receiving device 1630 using apacket communications technique. The network simulating circuit 1612modifies the voice packets PI into voice packets PA using theinformation IT and DT.

The local voice decoding circuit 1613 produces voice information ST1 bydecoding the voice packets PA. This voice information ST1 is sent to thecommunications quality judgement circuit 1614. A circuit which has thesame construction as the communications quality judgement circuit 1614may be used as the local voice decoding circuit 1613.

The communications quality judgement circuit 1614 evaluates the qualityof the voice information SI using the voice information ST1, Like thecommunications quality judgement circuit 535 (see FIG. 5).

The packet receiving device 1630 comprises a voice packet adjustmentcircuit 1631 and a voice decoding circuit 1632.

The voice packet adjustment circuit 1631 adjusts the voice packets PI;i.e., this circuit 1631 detects drop-out, makes the period uniform, andinserts substitute packets. Furthermore, the voice packet adjustmentcircuit 1631 outputs voice packets PO obtained by these adjustments. Inaddition, the voice packet adjustment circuit 1631 transmits drop-outpattern information IT and substitution pattern information DT using apacket communications technique.

The voice decoding circuit 1632 produces voice information S byextracting and decoding the voice packets PA.

The overall operation of the communications device 1500 of the presentembodiment will be described below.

First, voice packets PI are output to the network 1620 and networksimulating circuit 1612 from the voice encoding circuit 1611. The voicepackets PI being output to the network 1620 are received by the voicepacket adjustment circuit 1631. The voice packet adjustment circuit 1631adjusts the period of the voice packets PI, and inserts substitute dataif necessary. As a result, voice packets PO are produced. In additionthe voice packet adjustment circuit 1011 produces drop-out patterninformation DT and substitution pattern information IT, forms thisinformation into packets, and outputs these packets. The information DTand IT is sent to the network simulating circuit 1612 via the network1620. The voice decoding circuit 1632 produces voice information S byextracting and decoding the voice information of the voice packets PO.The voice information S is output to the outside of the packet receivingdevice 1630.

The network simulating circuit 1612 modifies the voice packets PI usingthe information DT and IT received from the network 1620. The method ofmodification is that same as in the fifth embodiment (see FIG. 14). Thevoice packets PA obtained as a result of this modification are convertedinto voice information ST1 by the local voice decoding circuit 1613. Thecommunications quality judgement circuit 1614 evaluates the voicequality by comparing the voice information SI and the voice informationST1. The results of this evaluation are output from the communicationsquality judgement circuit 1614 as a voice quality index E.

In cases where bi-directional communications are performed via a network1620 such as the internet or the like, the same route, and therefore thesame router, is used for communications via the outbound and returnpaths. Accordingly, in cases where packet drop-out and delay occur as aresult of the processing capacity of the switches in the router, thecommunications quality on the outbound path and the communicationsquality on the return path are the same. As was described above, anordinary voice packet communications device is equipped with both apacket transmitting device and a packet receiving device. Accordingly,in cases where the communications quality on the outbound path and thecommunications quality on the return path are the same, there is no needof the packet transmitting device to evaluate the communicationsquality. However, in cases where packet drop-out and delay occur as aresult of the processing capacity of the ports in the router, thecommunications quality on the outbound path and the communicationsquality on the return path are not necessarily the same. The reason forthis is that the ports used for the outbound path and the ports used forthe return path are different. In the present embodiment, in cases wherethe communications quality on the outbound path and the communicationsquality on the return path are different, the packet transmitting devicecan judge the communications quality of the transmitted voice packetsobjectively and in real time.

In addition, the communications system 1600 of the present embodimentmakes it possible to evaluate the communications quality while takinginto account the effect on this communications quality of drop-out thatoccurs when compressed data is extracted, without transmittinguncompressed data via the network 520.

The communications system 1600 of the present embodiment is useful inthe development, operation, maintenance and the like of voicecommunications systems.

Eighth Embodiment

A eighth embodiment of the present invention will be described withreference to FIG. 17.

FIG. 17 is a block diagram which illustrates the construction of thevoice packet communications device 1700 of the present embodiment. InFIG. 17, constituent elements that are labeled with the same symbols asin FIG. 16 respective indicate constituent elements that are the same asin FIG. 16.

The packet transmitting device 1710 has a local reference voice decodingcircuit 1711. The local reference voice decoding circuit 1711 producesvoice information SR by decoding voice packets PI. This voiceinformation SR is sent to the communications quality judgement circuit1614.

The overall operation of the communications device 1700 of the presentembodiment will be described below.

As in the seventh embodiment, the voice information SI is converted intovoice packets PI by the voice encoding circuit 1611. These voice packetsPI are output to the network 1620, network simulating circuit 1612 andlocal reference voice decoding circuit 1711.

The voice packets PI that are output to the network are received by thevoice packet adjustment circuit 1631. The voice packet adjustmentcircuit 1631 adjusts the period of the voice packets PI, and insertssubstitute data if necessary. As a result, voice packets PO areproduced. In addition, the voice packet adjustment circuit 1631 producesthe drop-out pattern information DT and substitution pattern informationIT shown in FIGS. 12 and 13, forms this information into packets, andoutputs these packets. The voice decoding circuit 1632 produces voiceinformation S by extracting and decoding the voice information of thevoice packets PO. This voice information S is output to the outside ofthe packet receiving device 1630.

The network simulating circuit 1612 modifies the voice packets PI usingthe information DT and IT received from the network 1620. The method ofmodification is the same as in the fifth embodiment (see FIG. 14). Thevoice packets PA obtained as a result of this modification are convertedinto voice information ST1 by the local voice decoding circuit 1613. Thelocal reference voice decoding circuit 1711 produces voice informationSR by decoding the voice packets PI.

The communications quality judgement circuit 1614 evaluates the voicequality by comparing the voice information ST1 and SR. The results ofthis evaluation are output from the communications quality judgementcircuit 1614 as a voice quality index E.

The communications system 1700 of the present embodiment can output,automatically and in real time, a communications quality index E thatobjectively expressed the communications quality. The communicationssystem 1700 of the present embodiment is useful in the development,operation, maintenance and the like of voice communications systems.

In the present embodiment, the packet transmitting device can judge thecommunications quality of transmitted packets automatically and in realtime in cases where the communications quality on the outbound path andthe communications quality on the return path are not the same. It isextremely useful to construct communications systems using thetechniques indicated in the first through eighth embodiments incombination. For example, by combining the fifth embodiment and thesixth embodiment, it is possible to perform both an evaluation of thecommunications quality that takes into account the effect on thiscommunications quality of information drop-out that occurs whencompressed data become to be extracted, and an evaluation of thecommunications quality that does not take this effect into account.

In cases where the present invention is used in multimediacommunications, an image data queue and a voice data queue can beinstalled inside the FIFO memory 203. In such a case, a functiondistinguishing between image data and voice data is required in theconstituent elements 201, 202 and 204 through 207 inside the voicepacket adjustment circuit.

There are no restrictions on the voice compression method used in thepresent invention. Lossly compression or lossless compression can beused as the compression method. However, the fourth, fifth and seventhembodiments are especially useful in cases where lossly compression isused.

The present invention can be applied not only to systems in whichbi-directional communications are performed, but also to systems inwhich uni-directional communications are performed.

1. A voice packet communications system, comprising: an adjustment meansfor evening out the periods of voice packets received from a network,detecting the dropouts of voice packets and counting the numbers ofdropped-out voice packets, or inserting substitute packets into thesequence of said voice packets, and outputting quality information thatcontains information that includes the number of dropped-out voicepackets, the number of substitute voice packets, or the number ofinternally accumulated voice packets; a decoding means for convertingsaid voice packets adjusted by said adjustment circuit into voiceinformation; and a judgement means for judging the communicationsquality of the voice packets using said quality information.
 2. A voicepacket communication system, comprising: an encoding means for producingvoice packets form voice information producing reference voice packetsfrom said voice information, transmitting said voice packets inaccordance with a protocol of the type in which quality is notguaranteed, and transmitting said reference voice packets in accordancewith a protocol of the type in which quality is guaranteed; a decodingmeans for converting said voice packets into voice information andconverting said reference voice packets into reference voiceinformation; and a judgement means for judging the communication qualityof said voice packets by comparing said voice information received fromthe network with said reference voice information received from thenetwork; wherein said encoding means is installed inside the packettransmitting device that transmits said voice packets and said referencevoice packets to said network, and said decoding means and saidjudgement means are installed inside the packet receiving device.
 3. Thevoice packet communications system according to claim 2; wherein saidvoice packets are compressed and said reference voice packets are notcompressed.
 4. The voice packets communications systems according toclaim 2; wherein said judgement means adjusts the period of the voicepackets.